High-frequency electric furnace



Oct. 18,1927. F GERTH 1,645,526

HIGH FREQUENCY ELECTRIC FURNCE Filed umh 24, 192'6 Parenteel oct. is, 1927.

UNITED STATES PATENT OFFICE.

FELIX GERTH, OF BERLINLTEMPELHOF, GERMANY, .ASSIGNOR T C. LORENZ AKTIEN'- GESELLSCHAFT, OF '.BERLIN-TEMPELHOF, GERMANY.

HIGH-FREQUENCY ELECTRIC FURNACE.

Application led Hatch 24, 1926, Serial No. 96,942, and in Germany, March 2p, 192.5.

The present invention relates to electric furnaces suitable for heating or melting metals and of the type in which hi h fre quency alternating current is passed trough l a heating coil located outside the Crucible, and the metal contained in the Crucible isv heated by the eddy currents generated therein. If, in such a furnace, the heating 1 is merely wound around the cylindrically l0 shaped Crucible 2, in the manner indicated in Figure 1 of the accompanying drawing, there is considerable marginal dispersion or fringing of the magnetic field, as indicated by the dotted lines in the drawings, with the result that a comparatively large percentage of the lines of force does not permeate the metal within the Crucible, thereby decreasing the efficiency of the furnace. It is the object of the present invention to overcome this disadvantage.

According to this invention the heating.

coil in a furnace of the type referred to is wound so that its turns decrease in diameter towards either or both of its ends, rendering it conformatory in contour to the Contour of the Crucible, the above-mentioned mar-- inal dispersion or fringing of the magnetic eld with respect to thevmetal to be heated in the Crucible is minimized, or in other Words, the energy expended in the Coil is to a greater extent concentrated upon the metal lo be heated.

In order that the invention may bevclearly understood and readily carried into effect, it will vnow be described more fully with `reference to Figures 2 to' 3 of the accompanying drawing, in which Figure 1 is a view in elevation, the coil appearing in section of a cylindrical Crucible with conventional Wind- 0 ing, illustrating the dispersion of themagnetic field which occurs with such a winding; Figure 2 is a vertical section through a Cylindrical Crucible with a winding in accordance with the principle Aof my invention; 5 and Figure 3 is a horizontal section throu h an elliptical Crucible with a winding embodgying the principle of my invention.

n the form of furnace depicted in Figure coil '2, the coil 1 is constituted by a cylindrical of the Crucible, thereby so dimensioning the turns with respect to those portions of the Crucible which they embrace that the created lines of force will be properly proportioned l and directed according to the transverse d1- mensions of that part of the Crucible which each coil turn envelops. The dotted lines in Figures 2 and 3 indicate lines of magnetic force, and it is seen that the number permeating the metal within the Crucible 2 is increased in comparison with those indicated in Figure 1, without any perceptiblefringing or marginal dispersion.

1. A high frequency electric furnace of the Character described comprising in combi nation a Crucible, and a heating coil embrac ing the Crucible and Wound so that at least certain of its turns decrease in diameter, rendering it conformatory in contour to the contour of the Crucible, whereby marginal dispersion or fringing of the magnetic field is minimized and the number of lines of force permeating the Crucible and producing the heating action is increased.

2. A high frequency electric furnace of the Character described, Comprising in combination an elliptical Crucible, and a heating coil embracing the Crucible and having its turns decreasing in diameter from the sides to'- wards the ends of the Crucible so as to conform` to the contour of the Crucible.

`In testimony whereof Ihave aiiixed my signature.`

ELIX GERTH 

